QuestionCan you tell me where to start looking for a short in the wiring. That would make the interior lights, keyless entry ,and the radio not work ? I tried to replace the fuse and it blows as soon as it makes connection. I love my car and would like to keep it, so please help.
AnswerHi Shirley,
Unfortunately there are a large number of bulbs and devices that are powered by that fuse. The fact that it blows means that some device/bulb/socket has an electrical bypass (short) from the fuse directly back to the battery which allows too much current to flow which blows the fuse. If you can get a hold of a volt-ohmmeter with a digital readout you could differentiate a low but finite resistance from a no resistance (shorting) condition. For the fuse not to blow the resistance that the fuse 'looks' at has to be more than 1.2 ohms. So with the meter you would go to the fuse box, and remove the fuse #13. The upper pin socket (labelled 25 perhaps) is the hot side which has 12V on it from the battery, so don't touch that one. The lower pin (labelled 26) is the one that is 'cold '(i.e. all the lamps and devices are attached to that one). If you set the meter to read ohms (20 ohm full scale) and touch the - lead of the meter to a shiney metal body surface and the + lead to the lower pin of the fuse socket it should read less than 1 ohm (because it will blow the fuse if you plug a new one into the socket).
Now the question is how to find which of the many items that are suspect is causing such a low reading. The courtesy light bulbs are the first to study:
Because almost all of those are not energized unless requested I would begin by attaching the meter leads mechanically to the fuse socket #26 (it may just wedge into the socket) and to a ground point (any shiney body metal) so that they are held in place without your holding them personally, and still with the meter in a position where you can read it. Then try closing all the doors and all the light switches that are hand controlled (e.g.,visor lamps if you have them for example), make sure the glove box and hood are closed, and then see if the meter changes to read more than 1.2 ohms or not, after waiting for 30 seconds. If it still reads less than 1 ohm, then presumably the wires to all the bulbs are not the source of the short. Then open a door and see if the reading drops below 1 ohm. If so then one of the many bulbs/sockets is the source of the short and you will have to remove the bulbs, one at a time, to find out which one is causing the meter to not stay above 1.2 ohms with and door open. That may solve the problem. If not:
Then the other possibilities need to be tested: the radio uses the fuse to store the presets for the radio stations (are you saying that the radio doesn't work at all or just that it has forgotten the preset channels?). You may have to remove the radio and unplug it to see if that is the source of the short. So we'll wait on that.
Do you have an automatic temperature type of A/C heater system? The small fan in the dash that blows the interior air across a temperture sensor (a small grill in the dash is the only clue for where that is) is also powered by fuse #13.
Do you have power mirrors? Those are supplied by fuse #13.
And the keyless entry module is also supplied by fuse #13.
The electrical switch that open the trunk lid is similarly supplied by fuse #13.
Unfortunately each of those item requires some disassembly to reach the plug which when removed will take it out of the circuit supported by fuse #13.
So before going into how to do each of those, why not try the lamps testing I began with and see what you learn. Then write back with the results. And try to recall anything about these various items that might have been acting up before the fuse blew, which would be an important clue.
Roland
Hi Shirley,
I can help you but it would be much more specfic if you could tell me which fuse is the one that is blowing? I suspect it is #13 (10 amp). Is that correct?
In addition, it will be much easier if you have a digital volt-ohmmeter to measure resistance in the circuit where the fuse blows (otherwise you just have to keep testing with a fuse which can be expensive). Such a meter can be obtained for about $20 at Radioshack or an electronics supply store. Ideally such a meter will have a full scale range setting of 20 ohms as a choice.
Basically you put the meter on the cold side of the fuse socket and measure the resistance from there to any shiney metal surface (ground = - post of the battery). You will find that it reads close to 0 ohms which is why it is blowing the fuse. Then I will suggest various plugs on the devices that draw from that fuse socket to remove to find which one has too low a resistance and is thus causing the fuse to blow. Then you figure out why the device has too low a resistance.
So let me know if it is fuse #13 and also do you recall any history when the fuse began to blow of a specific item that was acting up in around that point in time. If I am "maxed out" use the "thank and rate volunteer" tab where there is space to enter a comment.
Roland
